1. Field of the Invention
The present invention relates to the unambiguous detection of the presence of an object moving along a predetermined route and the determination of the direction of movement of such object. More specifically, this invention is directed to motion detection systems which discriminate between continuous motion of an object in a first direction and any other direction of movement of such object, the systems providing a warning signal commensurate with object motion in the first direction, and especially to systems of such character for energizing an alarm upon the unambiguous detection of vehicular traffic moving in a direction of interest. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
2. Description of the Prior Art
While not limited thereto in its utility, the present invention is particularly useful in the field of highway safety to provide a warning that a vehicle is entering a roadway traveling in a direction opposite to the normal traffic flow. There is a need, long unfulfilled, for a way of alerting motorists to the fact that they are about to enter a roadway traveling in the wrong direction and there is a concomitant longstanding need for means for alerting safety authorities and/or other motorists of the presence of a wrong-way vehicle. Obviously, the techniques and hardware for providing such warnings have applicability to other fields such as, for example, security systems.
Apparatus and techniques for detecting object motion and determining the direction of such motion are known in the art. Such known systems employ a source of radiant energy, i.e., ultrasound, light or microwave, and have found application in fields such as traffic light control and door openers. However, the previously known apparatus has not been suitable for the more demanding application, briefly discussed above, which the present invention is initially intended to serve. For use in the field of highway safety, it is exceedingly important that the alarm condition not be activated in response to false sensing, for example due to stray reflections of the radiant energy or movement of an animal. It is also desirable to be able to determine whether the vehicle operator has reacted to an activated "wrong way" alarm and has either ceased traveling in the improper direction or is, at least, decreasing the rate of travel in the wrong direction. Similarly, in order to be suitable for any traffic control purpose, a motion detection and discrimination system and technique must be highly reliable, have self-checking capability, be characterized by redundant testing for the occurrence of the alarm condition and have only modest power supply requirements. These characteristics are not critical in applications such as simple traffic light control and door openers and thus have not previously been available.